It’s a typical working day for Octavia Coates. But when it comes to lunchtime, instead of heading to the sandwich shop like her colleagues, she just grabs a large glass of water.

Lunch isn’t the only meal the ­34-year-old won’t be eating. Having had just a piece of fruit for breakfast, she won’t have anything until the following morning.

For one day a week, this office worker from King’s Lynn, ­Norfolk, doesn’t eat anything at all.

“I fast once a week and I feel ­amazing because of it,” she says.

And while her aim is to feel ­healthier and lighter, she could also be ­adding years to her life. There’s growing belief among ­scientists that fasting can improve long-term health, and reducing food intake over months or years could boost lifespan by 15% to 30%.

Findings from the Institute of Health ­Ageing at University College London suggest that eating 40% less could extend a person’s life by as much as 20 years. And the evidence seems to be mounting.

Last month a BBC Horizon documentary looked at the health benefits of part-time fasting, where a person eats normally for five days a week and fasts for the other two. By fasting, scientists recommend 500 calories or fewer for women and 600 for men.

But how does it work? Because, say the experts, when you starve yourself ­temporarily, your body switches from “growth mode” to “repair mode”.

Octavia started fasting part time by ­accident. “I was working in events ­organisation and spent one or two days a week running around on ­location,” she says. “Because I wasn’t sitting at a desk or near a kitchen, I never got round to eating that much.

“Weirdly, the next day I felt sharper, brighter and healthier. Then when I started a desk job I quickly gained weight, going from a size 8 to a 12.

“I felt tired, bloated and sluggish, so I decided to go back to having one or two days a week where I didn’t eat much.

“It worked. My weight ­stabilised, I felt less tired, had fewer headaches and much more ­energy.”

But Octavia doesn’t go completely without food on her fasting days.

“I’ll have a bit of fruit in the morning and a cup of coffee, then I’ll just have lots of water for the rest of the day,” she says. ­“Usually I drink a lot of coffee, but I only need one on my fast day because I feel more alert. I usually choose a day that I’m going to be busy at work and not out in the evening. I don’t ­exercise that day either.

“On a normal day, I’ll have scrambled eggs on toast with coffee. Lunch will often be a jacket potato with filling and for dinner I’ll have either a curry or a chicken salad, so I know I’m getting a wide range of nutrients when I do eat.

“I’m now a happy size 8 to 10, I never feel tired or ­bloated and my skin is clear. I feel great and I’ll fast like this for ever.”

“Experts are slowly starting to realise that, contrary to what we’ve always thought, fasting can improve your health. For a start, it allows your body to repair itself, which can potentially help us to live longer. When we fast the body is able to break down damaged cells and metabolise them.”

Another benefit is fewer calories, ­meaning you become leaner.

“Most of us eat too much and too often,” says Dr Carey. “However, our bodies are designed to lead a feast-famine lifestyle.”

It would seem that because our ancestors lived during a time when food shortages were a reality, they had to survive on very little food during leaner times. Biologically, we’re still able to do it.

“However, most of us now live in a ­feast-feast society where there’s an ­abundance of food – much of it fatty and sugary,” adds Dr Carey.

And studies show we’re eating more than ever, which is why as a nation we’re getting fatter and more prone to fatal diseases.

The University of Southern California found that occasional fasting can also reduce your risk of developing cancer.

Eating all the time is, according to Horizon’s Dr Michael Mosley, “like driving with your foot on the accelerator pedal, which is fine when your body is shiny and new, but keep doing this all the time and it will ­eventually break down.”

Fasting is also thought to improve brain health, too. Researchers at the National ­Institute on Aging in Baltimore, US, found that going through regular periods of ­fasting can protect the brain from ­degenerative ­diseases, like Alzheimer’s.

Fewer calories could be a brain booster according to ­Professor Mark ­Mattson, who worked on the ­Baltimore study.

“But it’s better to go on ­intermittent bouts of fasting, in which you eat hardly anything and then have periods when you eat as much as you like,” he says.

And Matthew Piper, who’s from the ­Institute of Healthy Ageing at ­University College London, says: “Studies on ­monkeys showed that if we restrict the diet there is a delay in the onset of cancer, coronary heart disease and ­diabetes in later life. It also staves off ­dementia.”

Another study, this time from the ­University of Illinois in Chicago, US, found that part-time fasting leads to better weight loss than daily dieting as it preserves lean muscle mass – which is sometimes lost through regular dieting – and burned off more fat than regular dieting, too. All this led to a more toned and leaner physique.

But Dr Carey adds: “It’s important to fast in a sensible and controlled manner and only do it one or two days a week at most.

“If you’re otherwise fit and well, then it’s perfectly safe, although I would advise ­seeking medical advice first – and make sure that you drink plenty of water during your fast day.”

But not everyone is that convinced. “I don’t think that occasional fasting makes a ­noticeable ­difference,” says ­nutritionist Ian Marber.

“While I agree that a low-calorie diet may elongate the life of cells, I don’t think you need to fast to achieve this.

“The idea that you need to give your body a rest from food, especially your digestive system, is rubbish.

“It doesn’t need a rest. It’s an organ like any other – your heart doesn’t need a rest, does it?

“Your digestive system – and your body – is perfectly capable of working every day because that’s what it’s designed to do.”

Marber also points out the impracticalities of part-time fasting and suggests that a busy mum or somebody working in an office or factory environment would find it too difficult to achieve.

He says: “Your blood sugar levels would end up dropping and you’d feel tearful, grumpy and find it hard to ­concentrate.”

Marber also points out that it could lead to unhealthy bingeing on the days you eat normally.

After all, if you’ve starved ­yourself all day you may be more likely to overindulge on all those biscuits, crisps and other fatty foods later on because you’re so hungry.

“Part-time fasting could also lead to an unhealthy binge-starve attitude towards food,” says Marber. “You could become a slave to it and have to juggle your diary around the days you don’t eat much. Who wants to live their life that way?

Marber does admit there’s some genuine weight behind the theory that it slows down natural cell death, which can help you live longer.

“But when a regular person starts to look into the tiny details of nutrition, they lose focus,” he says. “Yes, one or two days a week fasting may help you live longer, but I’d rather people just enjoyed a good, all-round ­balanced diet every day.”

Prophet Muhammad (pbuh) fasted twice a week Mondays and Thursdays. We Muslims fast other than just Ramdan too voluntarily.

One can fast one day one day off and repeat. Twice a week emulating the prophet (pbuh) how he did. Any day of the week, a number of days in a row.

I have a collection of articles on fasting and I didn't read this one until now. Thank you for sharing this amazing article.

It's funny how BBC ran a smearing article taking a jab at Muslims how we 'make' our children fast citing an example of a 10 year old that in fact voluntarily fasted. They should have ran an article on how children are 'made' to eat mcdonalds.

On a normal day, I’ll have scrambled eggs on toast with coffee. Lunch will often be a jacket potato with filling and for dinner I’ll have either a curry or a chicken salad, so I know I’m getting a wide range of nutrients when I do eat.